Objective The influence mechanism of different soybean meal addition on the water-resistant bonding strength and viscosity of modified cottonseed meal-based adhesive was clarified, which provided basis for industrial production and application of protein-based adhesive.

Method Using high-temperature dephenolized cottonseed meal, low-temperature defatted soybean meal and triglycidylamine as raw materials, the soybean meal modified cottonseed meal adhesive was synthesized on the basis of controlling the addition amount of soybean meal and the ratio of raw materials, and poplar plywood was prepared. The viscosity of adhesive was measured by rotary rheometer. The structure and morphology of the adhesive were characterized by Fourier transform infrared spectrometer, X-ray crystal diffractometer and scanning electron microscope. Thermogravimetric analyzer and universal mechanical tensile tester were used to analyze the thermal stability and bonding mechanical properties of the adhesive. Finally, the bonding strengthening mechanism of the modified adhesive was comprehensively analyzed.

Result With the increase of soybean meal content, the amount of lysine in the system increased, providing more active sites for cross-linking reaction, forming a mechanical interlocking effect of multiple crosslinking network structure, and improving the water-resistant bonding performance and toughness of the adhesive. When the addition of soybean meal is 10%, the dry strength and water-resistant bonding strength of adhesive TCM/SM10 are 1.24 and 0.79 MPa respectively. When the addition of soybean meal was increased to 30%, the dry bonding strength and water-resistant bonding strength of the adhesive were increased by 60.4% and 27.8% respectively compared with TCM, reaching 1.54 and 0.92 MPa, and the thermal stability and toughness were improved.

Conclusion In this study, low-temperature soybean meal is used to partially replace cottonseed meal for cross-linking modification to prepare cottonseed meal adhesive, which effectively improves the coating performance and water-resistant bonding performance of the adhesive, and provides a new idea for producing low-cost and high-performance protein-based adhesive.